Data/hora: 19/06/2024 04:40:08

Biblioteca(s): | Embrapa Cerrados.
Data corrente: | 25/03/1999
Data da última atualização: | 29/08/2014
Autoria: | KATO, M. do S. A.
Título: | Fire-free land preparation as an alternative to slash-and-burn agriculture in the Bragantina region, Eastern Amazon: crop performance and phosphorus dynamics.
Ano de publicação: | 1998
Fonte/Imprenta: | Gottingen: Cuvillier Verlag, 1998.
Páginas: | 144p.
ISBN: | 3897123479
Idioma: | Inglês
Notas: | Doctoral dissertation apresentada a Georg-August University, Gottingen.
Conteúdo: | Shifting cultivation is the most important agricultural land-use system in the Amazon region and the slash-and-burn practice is the traditional method for land praparation used by small farmes. Durin slash and burning, however, high amounts of nutrients are lost through volatilization. This fact, exacerbate by reduced fallow time, decreases the total nutrient stock of fallow systems and compromises the system's sustainability. The objectives of this study were: 1) to evaluate the effects of fire-free land preparation on crop performance and phosphorus dynamics; 2) to evaluate the importance of the use of chemical fertilizer in systems without the use of fire and 3) to select rice, cowpea and cassava cultivars suitable for mulch systems. The studies were conducted in the community of Cumaru in the municipality of Igarape Acu (Para, Brazil) on two neighboring sites with 4-year-old (FV4y) and 10-year-old fallow vegetation (FV10y). Three treatmenst for land preparation were tested with and without fertilizer. The treatments were: 1) burning + NPK fertilization; 2) mulching + NPK fertilization; 3) incorporation of the fallow vegetation biomass into the soil + NPK fertilization. Rice was planted followed by cowpea and cassava in two consecutive cropping periods. Yield characteristics of the crops as well as the phosphorus dynamics in the soil and uptake by the crops were evaluated. Furthermore, screening experiments were set up to evaluate the yield characteristic of a total of 8 rice maize, 21 cowpea and 5 casava cultivars under mulch conditions with and without fertilizer application. The land preparation experiment revealed that without fertilization, burning significantly increased the grain yields of rice in the first cropping period compared to cropping without burning. This result was most likely to the slow release of nutrients from the mulch or the incoporated plant material, possibly acerbated by nutrient immobilization, especially P. In the second cropping period, no differences in rice yield were detected in the  FV10y due to increased yields in the non-burned and non-fertilized treatment. Compared with the firts cropping period, with burning the rice grain yields showed an overall reduction of 7 in FV4y and 36% in FV10y in the second cropping period. The opposite offect may be noticed in systems without the use of fire; an increase in yilds of 117% and 233%, respectively, in the second cropping period compared to the first on could be observed. The yield increases in the second cropping period may be related to the liberation of nutrients through the decomposition of much. The use of fertilizers significantly increased the rice grain yields in the two cropping periods in both areas and erased the land preparation effect seen without the use of fertilizers. The cowpea yields without fertilizer were around 0.3 t ha in the burned treatments. When the field was not burned the yields were around 0.20 t ha in FV4y but cowpea did not produce at all in FV10y. With fertilization, cowpea grain yields were ariund 1.5t ha, regardless of the length of the fallow period and land preparation method. In the secon cropping period the greatest response in grain yield in relation to the first period were in the plots with mulch (with and without fertilizer). In the first cropping period cassava tuber yields were not influenced by land preparation, but residual fertilizer of the previously fertilized rice and cowpea crop doubled the yields. In the second period, without residual fertilizer, tuber, yields decreased in the burned plots by 30% and 34% in FV10, respectively. With residual fertilizer such a reduction was observed only in FV4y. In the non-burned treatments tuber yields were higher in FV4y than in FV10y. The total phosphorus uptake of the aboveground rice biomass in the first cropping period was 44% higher in FV10y than in FV4y, which is line with an increase of 52% in total rice biomass due to an improved nutrient supply in FV10y after burning. Given the fact that the P stock in the fallow vegetation of FV4y and FV10y were the same ( 9 kg ha), the uptake of P by rice has been soil derived rather than ash derived. In spite if the higher plant absorption observed in the burned treatments, the P utilization was higher the treatments that were not burned. In non-burned and non-fertilized plots the total P content of the cowpea pods was reduced by 50% in FV4y, compared to fertilized treatments. In FV10y this comparison connot be made because cowpea did not yield without fertilizer. P uptake not affected by the land preparation method when fertilizer was applied. The total amount of absorbed by cassava was similiar in FV4y and FV10y. Residual fertilizer of the previous rice and cowpea crop increased P uptake of cassava by 37% and 42% in FV4y and FV10y, respectively, in relation to the plants without fertilizer. The burning of the fallow vegetation significantly increased the pH of the soil as well as inorganic phosphorus (Pi) extractable with resin, and organic phosphorus (Po),, extractable with NaHCO3-, but without fertilizer application this increase, during cultivation, was only short-lived. Fertilization increased the P level in the soil. Without fertilizer, the levels of inorganic P decreased with time to pre-burn levels within 8 moths. The dynamics of resin-Pi and NaHCO3- Pi levels were synchronized with the dynamics of the less available NaOH-Pi fraction. The NaHCO3-Po pool was not affected by land preparation methods nor by the fertilizer treatment at either site. Regardless of the land preparation method, seasonal changes were observed in this fraction. The addition of crop residues contributed through its decomposition to an increase in the NaOH-Po level. This pool seems to be important for all P dynamics. NaOH-Po was the fraction that showed the highest shot-term increments as compared to other fractions. An increase in NaOH-Po was concomitant with a decrease in resin-and NaOH-Pi. The NaOH-Po seemed to be an indicator of the soil P and fertily status. The inorganic P fractions (resin, NaHCO3- and NAOH-) of the soil of sites were highly correlated with the available P determined in maize used as extractor plant in bioassay tests and with the rice, cowpea and cassava yields grown in the field. The plant bioassay P extracted from the soil by test plant and the microbial biomass P were reduced by burning when fertilizer was not applied. With fertilization, the differences between the available P levels of the burned and the non-burned plots were greater at FV10y than at FV4y. From the screening of cultivars suitable for the slash-and-mulch system without fertilizer use, only the rice cultivar CNA 7706 showed with a satisfactory productions level (39%) over the local cultivar ligeiro). It was not possible to identify any cultivar for either maize or cowpea able to offer satisfactory yields without the use of fertilizer. With fertilizer, the newly introduced rice cultivars yielded beteween 2.2 t ha to 3.0 t ha, with cultivars Progresso, Xingu and Araguaia standing out. The best yielding maize cultivars were Cincalli 93 SA3, Cincalli 93 Sa6, BR 5102, CMS 04C, CMS 39, CMS 50 and Saracura (2 to 3 t ha). The cowpea cultivars produced only fertilizer was used. The best performance showed TE 86-80-86F and TE 86-80-3G, with yields around 1.4 t ha. Cassava tuber yields were increased by residual effect from the fertilizer applied in the previous screening experiment (maize). The cultivars Mameluca, Pretinha, Aipim Rosa and Milagrosa seem suitable for shs-and-mulch sysytems. The fire-free land preparation appears to be viable technology for the nutrient-poor soil of the Eastern Amazon Region if fertilizers are applied to compensate for the loss of the fertilizing effect of the ashes from burning and the microbial immobilization of nutrients during the decomposition of the mulch layer. The availability of P was dependent on the decomposition of plant material (mulch or incorporated plant  material), reflectiong and increase in the production during the second cropping period. The results suggest that P was the limiting element to crop production.
Palavras-Chave: | Amazonas; Brasil; Land clearing.
Thesagro: | Cobertura do Solo; Cultivo Migratório; Fogo; Fósforo; Manejo do Solo; Performance; Planta; Queimada; Sistema de Cultivo.
Thesaurus Nal: | Brazil; burning; crop yield; cropping systems; fire ecology; shifting cultivation; slash; soil management.
Categoria do assunto: | --
Registro original: | Embrapa Cerrados (CPAC)
Exemplares: | CPAC - (15565-1) - ADD - LV - -- - 631.58 - K19f - 1999.00114 - DIS